The use and construction of balloon catheters is well known in the art. It is also well known to either attach a balloon segment adhesively to the end of a catheter or, alternatively, the balloon can be formed integrally with the catheter Such balloon catheters are described in U.S. Pat. No. Re. 32,983 to Levy and U.S. Pat. No. 4,820,349 to Saab.
It is also well known in the art to use balloon catheters in combination with guide catheters that assist in properly positioning the balloon catheter inside the body. Typically, the guide catheter is of a more rigid and durable construction than the balloon catheter. It may also have smooth, slippery or low friction surfaces to facilitate its movement through a lumen, such as a blood vessel, without causing trauma or tissue damage, until the distal end of the guide catheter is within a preselected distance, e.g., about 10 cm. or so, of the selected treatment area. The smaller diameter balloon catheter can then be threaded through the guide catheter until the balloon segment of the balloon catheter emerges from the distal end of the guide catheter proximate to the intended treatment site.
Alternatively, the balloon catheter can be positioned inside the guide catheter prior to insertion of the guide catheter into the body lumen, e.g., the blood vessel. In this procedure, once the distal end of the guide catheter is proximate to the selected treatment area, the balloon catheter is moved forward until all of the balloon segment has cleared the distal end of the guide catheter and is positioned at the intended treatment site.
Present balloon catheter technology employs balloons of fixed diameter and length. There are many medical procedures which employ balloon catheters which require a prior determination of the necessary length of the balloon in order to carry out the procedure. For example, in balloon angioplasty, the length of the diseased blood vessel is first determined. Usually, the surgeon determines in advance, for example through fluorscopic X-ray, ultrasound, and/or CAT scanning techniques, the approximate size of the area to be treated. Where only one length balloon is available (usually predetermined so that it will be, in most instances the size, and therefore usually shorter than the length of many diseased portions of blood vessel encountered in balloon angioplasty procedures) the surgeon will sequentially dilate different portions of the vessel extending the time and risks of the procedure. Where several catheters of differing balloon lengths are available, based upon observations by the surgeon, the surgeon will select a balloon length which will cover the entire length of the portion of the vessel requiring dilatation. If two or more blockage sites of different sizes exist within the same artery and the attending physician determines that two or more different sized balloons should be used, the surgeon may have to treat the most proximate site first, deflate and withdraw the first balloon catheter, and then insert a second balloon catheter having a balloon segment of a size commensurate with the size or location of the second obstruction or stenotic region that is going to be treated. Shorter balloons are often used to dilate lesions located on sharp bends in coronary arteries to prevent straightening and possible damage during the dilatation procedure. Longer balloons are employed to dilate large areas with extensive disease. Changing balloons, however, is a costly, time-consuming and potentially risky procedure that could lead to injury or death of the patient.
In addition, while it is believed the greatest use for balloon catheters is for treating profuse disease in blood vessels, and in particular diseased portions of peripheral and coronary arteries, there are certain other procedures where one of a plurality of catheters having different length balloons must be selected. For example, at least one prostate dilatation procedure requires the measurement of the prostate. The size of the balloon is the selected depending on the size of the prostate for which the procedure is being performed.
Thus, in the foregoing procedures, the surgeon must have catheters with various sized balloons on hand so that he can select the proper size balloon when performing the procedure.
Representative of the prior art in this field is U.S. Pat. No. 4,299,226 to Banka. The Banka patent discloses a method of dilating coronary arteries using a balloon-type catheter. The first step in the Banka method is to insert a "single lumen guide catheter 100 . . . so that the tip is positioned . . . within at least 20 cm., and preferably with (sic) 10 cm. of the blockage 300 to the dilated," (col. 3., lines 19-24 and FIG. 3). The second step in Banka is to thread a "double lumen balloon catheter 200 ... through the single lumen 101 of that guide catheter," (col. 3, lines 29-34 and FIG. 3). The result is that the dilation balloon 204 passes completely along the inside length of guide catheter 100 to emerge from the distal end of guide catheter 100 at a point within a predetermined distance from the arterial obstruction or stenotic region to be dilated. There is no suggestion in Banka that guide catheter 100 could be positioned or manipulated so as to prevent a portion of balloon 204 from dilating when in use.
U.S. Pat. No. 4,540,404 (Wolvek) is directed to a balloon catheter apparatus comprising a tapered distal end 12, a central lumen 38, and a balloon membrane 26 coaxial with and surrounding the central lumen and connected to the tip (FIG. 2A). According to the description in this patent, "a sheath 30 is slidable over the balloon to form an assembly . . . The sheath fits loosely over the balloon, whereby the sheath can be withdrawn to expose the balloon at the selected location and the balloon can then be inflated to provide therapy," (Abstract; FIG. 4). Furthermore, according to Wolvek, "Sheath 30 is sufficiently rigid to prevent the longitudinal collapse of the balloon membrane 26 as the (intra-aortic balloon) IAB 10 is inserted into the body and advanced along the artery," (col. 3, lines 65-68).
As in the Banka patent, there is no suggestion in Wolvek that sheath 30 could be positioned or manipulated so as to prevent a portion of balloon membrane 26 from dilating when in use. On the contrary, at col. 4, lines 52-55 and again at col. 5, lines 36-36, Wolvek states that, before dilation of the balloon, sheath 30 is withdrawn so that balloon membrane 26 is "completely uncovered". Furthermore, the frustoconical configuration of distal end 12, including a base portion 22 which "constitutes a shoulder facing in the proximal direction" (col. 4, lines 8-9 and FIG. 2A), "prevents the sheath 30 from overriding the distal end 18 of the tip 12 when pushed thereagainst . . . " (col. 4, lines 14-16). Thus, the Wolvek configuration restricts movement of sheath 30 in the distal direction.
U.S. Pat. No. 4,422,447 (Schiff) and U.S. Pat. No. 4,681,092 (Cho et al.) are directed to intra-aortic balloon catheters and to devices for "wrapping" the balloon portions prior to insertion of the catheters into the artery. In each of these patents, a sheath or sleeve portion (Schiff, FIG. 3, sheath 40; Cho et al., FIG. 6, sheath 56) is used to facilitate introduction of the balloon catheter into the artery.
The principal function of the sheath or sleeve portions in these patents appears to be maintaining the balloon sections in a tight, wrapped condition until the balloon sections are guided through the artery to the point of treatment. But, once the balloon section is delivered to the proper arterial location, the sheath or sleeve must be retraced (or the balloon must be advanced beyond the distal end of the sheath) such that the balloon section is completely uncovered and free to unwrap and dilate. If the sheath at this point continued to cover any part of the wrapped balloon, the balloon could not be fully or properly unwrapped and dilated for treatment purposes.
U.S. Pat. No. 1,852,351 (Lewis) is directed to a vaginal douche pipe comprising an external pipe 1, that serves as a housing and a control for an internal pipe 2 and for a soft, collapsible bulb 3. As illustrated in FIG. 3, during insertion of the apparatus into the vaginal canal, internal pipe 2, with deflated bulb 3 attached at its distal end, is housed inside external pipe 1. After insertion, internal pipe 2 is pushed forward thus permitting bulb 3 to be inflated unconstrained by external pipe 1 (See FIG. 4).
There is no suggestion in Lewis, however, that external pipe 1 could be positioned or manipulated so as to prevent a portion of bulb 3 from inflating. On the contrary, at col. 4, lines 99-107, Lewis states that the device is only ready to use when "internal pipe 2 is pushed forward . . . until the stock of stop cock of valve 4 reaches the right and left side slots . . . which retains . . . bulb 3 in an extended position as shown in FIGS. 2 and 4 . . . ".
These and other problems with and limitations of the prior art balloon dilatation catheters are overcome with the adjustable-length balloon catheters of this invention. Specifically, this invention obviates the need for catheter makers to produce multiple length balloons.